Start with the linear polynomial: $y = -3x + 9$. The $x$-coefficient, the root and the intercept are -3, 3 and 9 respectively, and these are in arithmetic progression. Are there any other linear polynomials that enjoy this property?
What about quadratic polynomials? That is, if the polynomial $y = ax^2 + bx + c$ has roots $r_1$ and $r_2,$ can $a$, $r_1$, $b$, $r_2$ and $c$ be in arithmetic progression?